1. Field of the Invention
The present invention relates to pressure relief valves of the poppet or lift valve type and more particularly to an improved valve seat.
2. Description of the Prior Art
Pressure relief valves of the poppet or lift type generally comprise an elongated valve housing having an outlet port disposed at right angle to its inlet end. The inlet end is provided with a valve normally maintained seated on a seat intersecting the inlet passageway by a spring axially biasing the valve toward its seat in which excess pressure, above a predetermined limit, unseats the valve by compressing the spring.
One commonly used commercial design employs a precision ball valve disposed in a huddling chamber and seating on a finely ground metal seat. This type of relief valve enjoys the economy of manufacture of a precision ball valve member mated with a spherical lapped seat. While economical in manufacture these valves suffer from a relatively short service life due to a rapid deterioration of both the ball valve and the lapped seating surface as a result of mechanical impact while reseating.
This invention provides a greatly improved seating means through unique construction which provides all the economies of a spherical-shaped valve member with the bubble tight qualities of a resilient precision seat. Service life expectancies are on an order of magnitude greater than that of conventional metal ball valves and seats. The uniqueness of the design in part lies in the molding of an elastomer to a metal surface which then maintains the cylindrical precision of a seating lip. Further, the geometry of the seating lip is such that fluid pressure tends to move the resilient lip into bubble tight closure with the spherical valve member. Moreover the metal huddling chamber with limiting surface may be constructed of a material substantially softer than the ball valve member without adversely affecting service life thus permitting further economies in construction.